Compilare: user.cpp: In function ‘bool isUpper(char)’: user.cpp:31:21: warning: array subscript has type ‘char’ [-Wchar-subscripts] return special[c] == 3; ^ user.cpp: In function ‘bool isLower(char)’: user.cpp:36:21: warning: array subscript has type ‘char’ [-Wchar-subscripts] return special[c] == 2; ^ user.cpp: In function ‘bool isDigit(char)’: user.cpp:41:21: warning: array subscript has type ‘char’ [-Wchar-subscripts] return special[c] == 1; ^ user.cpp: In function ‘int main()’: user.cpp:137:31: warning: ignoring return value of ‘char* fgets(char*, int, FILE*)’, declared with attribute warn_unused_result [-Wunused-result] fgets(aux, MAX_LINE+1, in); ^